Low-angle X-ray Diffraction Method Research Articles

Morphology, structure and photowettability of TiO2 coatings doped with copper and fluorine

The work reports synthesis, structure and properties of doubly doped titanium dioxide coatings activated by ultraviolet and visible light. Copper within a concentration range of 0.4–3.4at% and fluorine within a concentration range of 1.7–9.4at% were introduced as dopants. The coatings were prepared with the help of radiofrequency plasma enhanced chemical vapor deposition technique with a single precursor compound providing both dopants and titanium (IV) chloride being a source of titanium. Elemental composition and chemical bonding analyses of the coatings were carried out with the help of X-ray photoelectron spectroscopy. The results indicate that both admixtures are chemically bound to the TiO2 matrix – a notion confirmed by Fourier transform infrared spectroscopy. Phase composition studies, performed with a low angle X-ray diffraction method, revealed a presence of a threshold concentration of the dopants affecting the coatings crystallinity. Surface morphology and its topography were studied with the help of scanning electron microscopy and atomic force microscopy. Several coatings exhibited a superhydrophilic effect upon relatively short time of illumination.

Morphological and structural investigations of Co–MgF 2 granular thin films grown by thermionic vacuum arc

Co–MgF 2 granular films were deposited in thermionic vacuum arc plasma with simultaneous ignition of plasma in Co and MgF 2 vapours. The samples were investigated by transmission electron microscopy which revealed Co grains of a few nm in diameter embedded in the MgF 2 matrix. The crystalline phase for Co and MgF 2 was studied by electron diffraction after selecting a typical area of the sample. Low-angle x-ray diffraction method was used to verify the bulk crystalline structure of the samples. The surface morphologies of the films were investigated by atomic force microscopy. The magneto-optical longitudinal Kerr rotation spectra of the films were also measured and compared.

Modelling muscle motor conformations using low-angle X-ray diffraction

New results on myosin head organization using analysis of low-angle X-ray diffraction patterns from relaxed insect flight muscle (IFM) from a giant waterbug, building on previous studies of myosin filaments in bony fish skeletal muscle (BFM), show that the information content of such low-angle diffraction patterns is very high despite the 'crystallographically low' resolution limit (65 A) of the spacings of the Bragg diffraction peaks being used. This high information content and high structural sensitivity arises because: (i) the atomic structures of the domains of the myosin head are known from protein crystallography; and (ii) myosin head action appears to consist mainly of pivoting between domains which themselves stay rather constant in structure, thus (iii) the intensity distribution among diffraction peaks in even the low resolution diffraction pattern is highly determined by the high-resolution distribution of atomically modelled domain mass. A single model was selected among 5000+ computer-generated variations as giving the best fit for the 65 reflections recorded within the selected resolution limit of 65 A. Clear evidence for a change in shape of the insect flight muscle myosin motor between the resting (probably like the pre-powerstroke) state and the rigor state (considered to mimic the end-of-powerstroke conformation) has been obtained. This illustrates the power of the low-angle X-ray diffraction method. The implications of these new results about myosin motor action during muscle contraction are discussed.

The characterization and gas-sensing properties of a novel amphiphilic phthalocyanine LB film

The LB films of asymmetrically substituted 1,4-di(hydroxyethoxy)-9,10,16,17,23,24-hexapentyloxyphthalocyanine have been fabricated at different surface-pressures. The molecular packing of the films has been characterized by polarized UV-vis. absorption spectroscopy and low angle X-ray diffraction methods. The results show that the films have well-ordered structure and the molecular packing within the films is dependent on the film-deposition conditions such as surface-pressure. The gas-sensing behavior of the films to NO 2 gas has been investigated by conductance measurements. It is indicated that the films deposited at lower surface-pressure show larger and faster response and recovery kinetics.

Molecular Order within Langmuir−Blodgett Films of Two Amphiphilic Octasubstituted Phthalocyanines Studied by Atomic Force Microscopy

Y-type Langmuir-Blodgett films of the octasubstituted amphiphilic phthalocyanines 1 and 2 deposited onto hydrophobic glass have been investigated by atomic force microscopy (AFM). The technique has been used to measure the thicknesses of one, two, and three bilayer films, and the results show that each bilayer is of the same thickness. This characteristic thickness is the same as the repeat spacing measured using low-angle X-ray diffraction methods on thicker samples, and thus we demonstrate that the order of the molecules in the monolayers after several cycles of deposition remains constant. We have detected considerable differences with respect to the consistency of the films of 1 and 2 and their resistance to the pressure exerted by the AFM tip during the scanning process required to obtain the images. Films of 1 are more robust and we have observed the columnar arrangement of the molecules at the surfaces of one, two, and three bilayers. However, under the same imaging conditions it was not possible to observe molecular order before perturbing the surface of the films formed by 2. The lateral extent of the ordered regions at the surfaces of the films of 1 covers areas of at least 10 μm 2 . There is very clear evidence that there is a predominant alignment. Inspection of 82 images taken of different regions of the film indicates that ca. 83% show columns whose axes are aligned to within ±30° of the dipping direction.

Monolayer behaviour and Langmuir–Blodgett film properties of some amphiphilic phthalocyanines: factors influencing molecular organisation within the film assembly

The monolayer and LB film-forming properties of 20 structurally related amphiphilic octa-substituted phthalocyanine derivatives have been assessed. The molecular packing within examples of the films has been probed by visible-region spectroscopy and low-angle X-ray diffraction methods. Among derivatives where the aliphatic substituents are attached by ether linkages, there is a variation in the behaviour according to the length of the chains and whether or not the chains are branched. Films are not highly ordered but may contain domains of ordered structure, giving rise to a red-shifted absorption band in the visible spectrum. Analogues where the chains are attached by carbon–carbon bonds show superior monolayer behaviour and are excellent materials for deposition as LB films. Furthermore, there is good evidence from the spectra that change in the length of the alkyl chains provides a means of controlling the type of molecular packing within the films.

Transformation between Lamellar and Nonlamellar Aggregates Formed with Synthetic Peptide Lipids

Abstract The morphological behavior of various combinations of the following synthetic lipids was investigated in the aqueous dispersion state by means of electron microscopy, differential scanning calorimetry, and fluorescence polarization spectroscopy as well as by turbidity and X-ray diffraction measurements: N+C5Ala2Cn and N+(H)C5Ala2Cn as cationic, (SO3−)C5Ala2Cn as anionic, and QC5Ala2Cn as nonionic (n=14, 16). Aqueous dispersions of various combinations of cationic and anionic lipids at the equimolar ratio afforded nonlamellar aggregates, having highly ordered and three-dimensional network structure with repeating distances in the 70–130 Å range, above their phase transition temperatures (Tm). However, any slight loss of the fractional balance retained at the equimolar ratio led to the formation of bilayer aggregates. Under such conditions that allow the formation of nonlamellar aggregates, the high microscopic homogeneity of cationic and anionic lipid molecules was attained, originating from the intramembrane electrostatic interaction between cationic and anionic head moieties to form highly developed ion-pair clusters on the aggregate surface. Meanwhile, the nonlamellar phase appeared above Tm was spontaneously transformed into the normal bilayer phase below Tm as confirmed by electron microscopy and turbidity measurements. The nonlamellar phase was also characterized by the low-angle X-ray diffraction method and was consistent with the highly developed domain with the face-centered cubic lattice.

スパッタ法で作製したアモルファスＺｒ‐Ｆｅ／Ｔｂ‐Ｆｅ組成変調多層膜の磁気特性

Magnetic and magneto-optical properties of amorphous Zr-Fe/Tb-Fe composition modulated multilayered films (CMF) prepared by RF sputtering technique were investigated. In this system, a composition modulation period (D) more than 40 Å was confirmed by the low angle X-ray diffraction method. Curie temperature (Tc) of these multilayered films falls with decreasing D, but saturation magnetization (Ms) and perpendicular anisotropy (Ku⊥) increase with decreasing D. Sharpening of hyperfine field distribution was observed with the decrease of D. Wavelength dependences of magneto-optical Kerr rotation (θK) are independent of the variation of D.

A low-angle X-ray diffraction analysis of osteonic inorganic phase using synchrotron radiation

Using synchrotron radiation the low-angle X-ray diffraction method has been applied to single osteon samples to yield new data on the texture of the inorganic bone fraction. Two sample types--cylindrically shaped osteonic samples and osteonic radial hemisections--were prepared from longitudinal and alternate osteons at both the initial and final stages of calcification. The results indicate that the diffraction pattern is due to the inorganic phase, which reveals the same axial periodicity as native collagen fibrils and fits into the main band. No change is appreciable as osteons pass from the initial to the final stage of calcification. This means that when crystallites covering much more than a collagen axial period are observed under the electron microscope, they do not appreciably affect the calcified banding of collagen fibrils. The osteonic axis corresponds to the main direction of collagen orientation both in longitudinal and alternate osteons. The degree of orientation, however, is lower in alternate osteons than in longitudinal ones, where only few thin, incomplete transversal lamellae are found.

Chemical — Physical characterization of aluminas in the car exhaust gas treatment

To characterize the crystalline compounds used as active catalytic supports, in the oxidizing catalysis of the combustion engine unburnt exhaust gases and their physical and chemical transformations induced by heat treatment, 3 types of γ-Al 2O 3 base oxidizing granular catalysts have been considered. Qualitative and quantitative analysis of the samples have been carried out both through X-ray diffraction and with the neutron activation technique. The samples have been subjected to ageing at 1100°C in order to cause degradation (verified through X-ray diffraction) of the active support catalytic properties. Later on, through low-angle X-ray diffraction method, the O s specific internal surface has been measured for each sample. From the experimental results it is pointed out: 1. 1) the excellent stability of catalysts containing BaCO 3 can be noticed from the γ-Al 2O 3→ α-Al 2O 3 transformation, which occurs through successive degradations and rearrangements of so-called “transition aluminas”; 2. 2) the sudden decrease of the specific internal surface owing to the heat treatment. This decrease, compared with the dimension variation (440) of crystallites, allows to assume that a first short stage of disoriented crystalline strong coalescence occurs followed by a steady growth of the isoriented crystalline dimensions.

Supramolecular structure and incipient cracks in three-dimensional stitched amorphous polymers

The electron-microscopic method was used to study the structure of unsaturated polyester films. The initial submicrocracks developing in the loaded films were studies by the low-angle x-ray diffraction method. It is shown that for these polymers a typical feature is the globular structure with a globule diameter of 103–3·103 A, and the transverse dimension of the submicrocracks developing under the action of a load practically coincides with the globule diameter.

Low angle x-ray diffraction and biology

The use of the low-angle x-ray diffraction method in biology is described. Some x-ray diffraction patterns have been known since the early 1930's but, in the last decade, many new patterns, which show more reflections than previously, have been recorded. An interpretation of these improved patterns of biological systems provides detailed information on the molecular structure of living cells. The theory and the current status of the low-angle x-ray diffraction method is presented. A brief account of the x-ray studies on collagen, muscle, nerve and membranes is given. Emphasis is given to the history of ideas underlying progress in this area and the current unsolved problems in this field of biophysical research are indicated and discussed.